Communication systems typically include a plurality of communication units, such as mobile or portable radio units, dispatch consoles and base stations (sometimes called base site repeaters) that are geographically distributed among various base sites and console sites. The radio units wirelessly communicate with the base stations and each other using radio frequency (RF) communication resources, and are often logically divided into various subgroups or talkgroups.
Communication systems are often organized as trunked systems, where the RF communication resources are allocated on a call-by-call basis among multiple users or groups. Wide-area trunked systems are sometimes organized into a plurality of “zones,” wherein each zone includes multiple sites and a central controller or server (“zone controller”) for allocating communication resources among the multiple sites. The zone controller(s) may reside within a single device or multiple devices and may be located at a fixed equipment site or may be distributed among various base sites. The RF resources may comprise, for example, narrow band frequency modulated channels, wideband modulated signals, broadband modulated signals, time division modulated slots, carrier frequencies, frequency pairs, or generally any medium for communicating information, such as voice, video, or data traffic (“payload information”) or control signaling (“control information”) to and from participating communication devices over wireless link(s).
In recent years, communication systems have been implemented using packet-switched technology where information that is to be communicated between endpoints is divided into packets and transported by various routers forming an Internet Protocol (IP) network. Packet-switched networks are sometimes called “connectionless” networks because they do not provide dedicated bandwidth or circuits between endpoints, but rather permit communications between multiple endpoints to proceed concurrently over shared paths or connections. The endpoints (or “hosts” in IP terminology) may comprise, for example, base stations, consoles, routers, zone controllers, and in some instances, wireless mobile or portable radio units in different zones that desire to receive packets for a particular call. In such systems, the participating hosts send Internet Group Management Protocol (IGMP) Join messages to attached routers, causing the routers of the network to create a spanning tree of router interfaces for distributing packets for the call.
Due to the “connectionless” nature of IP packet-based networks, it is possible to over-subscribe certain links including, but not limited to, inter-zone links between multiple hosts. Generally, in any packet-based system, over-subscription of link(s) causes delays in transport of IP packets that adversely effect the quality of service of the network. The problem is most acute in large systems including multiple hosts distributed among several sites and/or zones. In such systems, inter-zone links between remote hosts are usually leased by communication system customer(s). Understandably, customers demand a certain quality of service and are more willing to occasionally queue (or “busy”) inter-zone calls due to insufficient resources than to pay extra recurring costs to overprovision these links to accommodate peak traffic loads. Accordingly, there is a need for a method of admission control in an IP packet-based communication system that provides for establishing calls over shared links of an IP network without exceeding available bandwidth.
One manner of addressing these needs is described in related patent application Ser. No. 09/891,645, wherein reservations of bandwidth are established dynamically (i.e., on a call-by-call basis) for certain links by a certain host devices (termed reservation proxy elements, or RPEs) on behalf of other participating hosts (e.g., base stations, etc.) that may require use of bandwidth. The reservations of call units are established by the RPEs using standard ReSerVation Setup Protocol (RSVP) signaling using multicast group address(es) that are used for actual calls. The RPEs join a multicast group address that is to be used for a call and exchange RSVP signaling messages across one or more inter-zone, packet network links to reserve communication resources for the call on behalf of participating devices in various zones. The RPE function may reside within the zone controllers or separate infrastructure device(s) of different communication zones.
Advantageously, the reservation proxy operation enables bandwidth reservations made by the RPEs to be exploited by other hosts of the network without the need for separate RSVP transactions, and hence without additional network loading. A problem that arises, however, is that the operation described in the Ser. No. 09/891,645 application does not provide for the RPEs to specify any filtering of multicast traffic. Consequently, the RPEs (while joined to the multicast group address) will continue to receive all payload and control information directed to the multicast group address even though, generally, it is undesirable for the RPEs to receive payload information since this negatively impacts in control processing capacity. Optionally, the RPEs may leave the multicast group address after establishing the RSVP reservations so as to discontinue receiving payload information, but this will also result in discontinuing control information that may be necessary for the RPEs to perform further resource management or control functions for the call.
For example, roaming of radio units between different communication zones may occur such that new links need to be established (or old links torn down) during a call. Typically, the location of the radio units is tracked by zone controller(s) and, if necessary, changes are communicated to other zone controllers and/or RPEs via control messages. If any RPEs were to leave the multicast group address after establishing the RSVP reservations for a particular topology, they would be unaware of the new topology and thus would be unable to accommodate resource management functions for the new topology. This problem would occur whether the RPEs reside within one or more zone controllers (e.g., upon certain zone controller(s) no longer being able to track location, or no longer exchange control messages with other zone controllers) or within separate devices (e.g., upon the RPEs no longer receiving control information from zone controllers).
Accordingly, there is a need for a reservation proxy operation whereby RPEs make bandwidth reservations on behalf of other hosts in the network, but which allows the RPEs to specify filtering of multicast traffic. Advantageously, the reservation proxy operation will enable RPE/zone controllers to receive desired control information for the duration of the call without being encumbered by undesired payload information. The present invention is directed to addressing these needs.